Given his concerns about feeding lead to his family, almost definitely he means solid copper. Modern lead-free solid copper bullets work quite well for many animals. Here's a sample article comparing them against traditional copper jacketed lead: https://www.guns.com/news/2017/03/18/do-copper-bullets-offer...
Surely you mean copper-jacketed lead, right? I don’t think that solid copper bullets would travel very far or carry much of a punch …